Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 14 2008 10.5194/acp-8-4019-2008 http://www.atmos-chem-phys.net/8/4019/2008/ http://www.atmos-chem-phys.net/8/4019/2008/acp-8-4019-2008.html http://www.atmos-chem-phys.net/8/4019/2008/acp-8-4019-2008.pdf 4019 4026 2008-07-25 Correlation between equatorial Kelvin waves and the occurrence of extremely thin ice clouds at the tropical tropopause F. Immler franz.immler@dwd.de K. Krüger M. Fujiwara G. Verver M. Rex O. Schrems Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany IFM-GEOMAR, Kiel, Germany Hokkaido University, Faculty of Environmental Earth Science, Japan Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany now at: Richard Aßmann Observatory, Lindenberg, German Meteorological Service (DWD), Germany A number of field-campaigns in the tropics have been conducted in recent years with two different LIDAR systems at Paramaribo (5.8° N, 55.2° W), Suriname. The lidars detect particles in the atmosphere with high vertical and temporal resolution and are capable of detecting extremely thin cloud layers which frequently occur in the tropical tropopause layer (TTL). Radiosonde as well as operational ECMWF analysis showed that equatorial Kelvin waves propagated in the TTL and greatly modulated its temperature structure. We found a clear correlation between the temperature anomalies introduced by these waves and the occurrence of thin cirrus in the TTL. In particular we found that extremely thin ice clouds form regularly where cold anomalies shift the tropopause to high altitudes. These findings suggest an influence of Kelvin wave activity on the dehydration in the TTL and thus on the global stratospheric water vapour concentration. Boehm, M. and Verlinde, J.: Stratospheric influence on upper tropospheric tropical cirrus, Geophys. Res. Lett., 27, 3209–3212, \doi2000GL011678, 2000. Bonazzola, M. and Haynes, P H.: A trajectory-based study of the tropical tropopause region, J. Geophys. Res., 109, D20 112, \doi10.1029/2003JD004356, 2004. Comstock, J M., Ackerman, T P., and Mace, G G.: Ground-based lidar and radar remote sensing of tropical cirrus clouds at Nauru Island: Cloud statistics and radiative impacts, J. Geophys. Res., 107, 4714, \doi10.1029/2002JD002203, 2002. 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